Field of the Invention
This invention relates to a field for imaging wall thickness variations, changes in tubing, imaging casing through a tube, and imaging multiple tubes using non-destrctive means in cased-hole downhole logging applications. The changes and variations of tubing walls may be caused by internal and/or external patches, clamps, corrosions, errosions, and/or any combination thereof.
Background of the Invention
Tubing may be used in many different applications and may transport many types of fluids. Many times tubes may be placed underground and/or positioned in an inaccessible area, making inspection of changes within tubing difficult. It may be beneficial to measure the thickness variations within a tube while the tube is in use. Previous methods for inspecting tubes have come in the form of non-destructive inspection tools such as electromagnetic devices that may measure magnetic flux-leakage within tubing, which may not be able to detect changes in multi-pipe situations. Additionally, previous methods may not be able to perform multi-pipe azimuthal imaging. Electromagnetic devices may be well suited for tube inspection because they may operate and be insensitive to any fluid within the tube.
Previous devices and methods that may measure flux-leakage may only be useful for the detection of localized damage in ferromagnetic pipes. The measurement of flux-leakage may be hindered by the type of tube, thinning of tubing, requirements of a strong magnetic field, strong flux coupling, and a requirement for the device to be in close proximity to the tube walls. Additionally, electromagnetic tools that use eddy-current may be better suited for measuring the integrity of tubing. Drawbacks of a constant eddy-current electromagnetic tool may be that the signal from several frequencies may not penetrate a first wall of tubing and allow inspection of the integrity of a second wall of a larger surrounding tubing. Transient electromagnetic methods using pulsed electromagnetic waves may be limited to increasing the signals from a second tube wall to additional tube walls, have problems optimizing a receiver coil, and may suffer Signal-to-Noise Ratio problems.
Consequently, there is a need for an electromagnetic tool which may induce a larger amount of eddy-current within surrounding pipe walls. In downhole applications, multi-piping wall variation imaging detection capability may be in high demand. Demands may include locating clamps of permanent waveguide production monitering wells for muti-perforations, through-tubing casing deformation measurement, tube eccentricity within casing, and imaging of corrosions for multiple pipes.